A variety of compass assemblies for forming circles about a given stationary point are known. These include conventional compass structures with v-shaped frames which are hinged at their apexes. Pointed stylus tips and/or sharp marking instruments are secured to the frames of these structures at different locations. In some assemblies, the marking instruments are inserted into short cylinders integrally formed with or otherwise attached to the v-shaped frames. The marking instruments are then retained within the cylinders by hinged elements.
While the above-described compasses provide means for forming circles on a given surface, there are problems associated with their use. For example, the hinged frames of conventional compasses readily loosen at their apexes. Because the pointed tips and the marking instruments (which are attached to the sides of the frames) are maintained in a predetermined spacing during usage, any undesired lateral movement within the frame structures results in the formation of asymmetrical circles. Since conventional frames do not include mechanisms for tightening the hinges of the frames, the compasses are often rendered useless as the hinges loosen over time.
Also, the elements which secure the marking instruments to the frames of conventional compasses frequently weaken with use. This, in turn, permits the marking instruments to drift axially during use. Such axial movement similarly interferes with proper usage of the compasses and may render the compasses inoperative.
Finally, conventional compasses cannot be disassembled during nonuse. Because compasses usually have sharp marking instruments and/or pointed stylus tips, they are potentially hazardous if stored in an assembled state.
Accordingly, an object of the present invention is to provide an improved compass for forming circles which does not employ V-shaped frames but generally includes a simple two-piece construction.
It is another object of the present invention to provide an improved two piece compass for forming circles which holds marking instruments with bottom portions in alignment with one another when the instruments are rotated to a zero radius position, and top portions which do not intersect one another when the marking instruments are rotated to increase the radii of the circles.
It is another object of the present invention to provide an improved compass for forming circles which restricts undesirable lateral and axial movement of the drawing instruments within the compass body during use.
It is another object of the present invention to provide an improved compass for forming circles which includes a stylus that is adjustable in length to accommodate drawing instruments that are shortened due to frequent sharpening.
It is yet another object of the present invention to provide an improved compass for forming circles which allows for the easy rotation of the marking instruments towards and away from one another.
It is a further object of the present invention to provide an improved compass for forming circles that is relatively inexpensive to manufacture.
Other objects and advantages of the invention will appear hereinafter.